In cam looms now in general use, a plurality of cams are carried in fixed relation to a rotatable auxiliary cam shaft. Such cams are specially designed to effect movement of Longitudinal treadles associated with respective harnesses in a predetermined timed sequence to produce a fabric in accordance with the concept of the designer of the fabric. A major problem arises when altering the cams to produce fabric according to a different design, especially if the new design is complex, since the cam configuration and arrangement on the auxiliary cam shaft must be changed often requiring the purchase of new and specially designed cams to carry out a sequence of harness operation called for by the new design being woven. Although large stocks of cams of varying designs are maintained by most mills, the fabric designs are, nevertheless, limited by the cam configurations which are available. The designing and setting of such shedding cams requires a high degree of skill as well as time consuming labor.
In connection with the more complicated fabric designs, complex cam constructions are necessitated utilizing relatively short periods of change and dwell producing jerky harness operation which causes excessive wear on the harness straps and mechanisms associated with the operation of the harnesses. Pick timing is limited because with each revolution of the auxiliary cam shaft, the harness associated with a given cam must be raised and lowered at least one time.
Many efforts have been made to solve these problems, including the provision of individual motors to raise and lower each harness in a predetermined sequence. U.S. Pat. No. 1,648,011 illustrates the use of individual chains for intermittently driving individual cams, but such structure is exceedingly complex and is more similar to a Dobby loom than to a cam loom. The cam surfaces are in the form of internal tracks carried within the sprockets.
Accordingly, it is an important object of this invention to provide a novel cam arrangement wherein co-acting means carried by individual chain drives may be easily changed or re-arranged to produce any desired movement and timing of the cam associated therewith.
Another important object of this invention is the provision of individually driven, simple cams so that the changes are less precipitous resulting in a smooth harness motion minimizing wear on associated loom parts. Such shedding action permits high production speeds and a minimum of ends down. Since the drives are individual and intermittently drive the cams, loom operation may be carried out with less power consumption.
A very important object of the invention is the provision of a smooth cam loom harness motion permitting high speed loom operation even when weaving complicated fabric constructions as may normally be woven upon a Dobby loom.
Another object of the invention is to provide cams rotatably mounted on a fixed shaft with individual chain drives permitting simplified cam construction and yet providing a great variety of harness timing motions so as to permit a wide variety of fabric designs to be woven.
Still another important object of the invention is the provision of a method for operating harnesses wherein simple cams are moved intermittently responsive to a timing mechanism operating the cams on an individualized basis on a fixed shaft to operate longitudinal treadles.